Potent and Selective Peptide-based Inhibition of the G Protein G?q.

ABSTRACT: In contrast to G protein-coupled receptors, for which chemical and peptidic inhibitors have been extensively explored, few compounds are available that directly modulate heterotrimeric G proteins. Active G?q binds its two major classes of effectors, the phospholipase C (PLC)-? isozymes and Rho guanine nucleotide exchange factors (RhoGEFs) related to Trio, in a strikingly similar fashion: a continuous helix-turn-helix of the effectors engages G?q within its canonical binding site consisting of a groove formed between switch II and helix ?3. This information was exploited to synthesize peptides that bound active G?q in vitro with affinities similar to full-length effectors and directly competed with effectors for engagement of G?q A representative peptide was specific for active G?q because it did not bind inactive G?q or other classes of active G? subunits and did not inhibit the activation of PLC-?3 by G?1?2 In contrast, the peptide robustly prevented activation of PLC-?3 or p63RhoGEF by G?q; it also prevented G protein-coupled receptor-promoted neuronal depolarization downstream of G?q in the mouse prefrontal cortex. Moreover, a genetically encoded form of this peptide flanked by fluorescent proteins inhibited G?q-dependent activation of PLC-?3 at least as effectively as a dominant-negative form of full-length PLC-?3. These attributes suggest that related, cell-penetrating peptides should effectively inhibit active G?q in cells and that these and genetically encoded sequences may find application as molecular probes, drug leads, and biosensors to monitor the spatiotemporal activation of G?q in cells.

SUBMITTER: Charpentier TH 

PROVIDER: S-EPMC5207258 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature